1) Field of the Invention
The present invention relates to an integrated circuit chip module that is provided with an EMC (electromagnetic compatibility) measure, that is, EMI (electromagnetic interference) and EMS (electromagnetic susceptibility) measures.
2) Description of the Related Art
An integrated circuit chip module is structured, in many cases, as a multi-chip module that has a plurality of integrated circuit chips mounted on a printed wiring board. For example, a portable telephone has various kinds of circuits mounted within a case of a very small installation area and a very small installation capacity. These circuits include a circuit that carries out a signal processing of a voice signal, an image signal, and a data signal, a control circuit, a circuit that transmits and receives a signal by converting it into a wave, and a liquid crystal display circuit. In order to provide these circuits in light, thin and small structures, a method of mounting these circuits as a multi-chip module has been employed. The integrated circuit chip module is also used in a portable terminal, and a camera-integrated video apparatus, for the same reason of light, thin and small structures. Further, the integrated circuit chip module is also used in a computer that requires high-speed operation, and a transmitter/receiver and a measuring apparatus (a front-end circuit of a probe) that uses an ultra-high-frequency band (GHz band).
For example, when a portable telephone transmits in real time a moving picture picked up by a mounted image pick-up device, the portable telephone executes a transmission/reception of voice as well as a transmission/reception of the images obtained by the image pick-up devices while emitting a wave. At this time, the wave emitted from the portable telephone incurs an electromagnetic induction to other internal circuits mounted on this portable telephone. Therefore, this electromagnetic induction might bring about errors in the operation of these other internal circuits.
The erroneous operation includes such phenomena as an inclusion of a stripe pattern in the picked-up image, a distortion of the picked-up image, an abnormal reproduction of colors in the picked-up image, and a reduction in the signal-to-noise ratio of the picked-up image. Further, through-current noise that is intrinsic to a CMOS digital circuit generated in a digital signal processing circuit within the portable telephone may flow into an image processing circuit through a power source wire, and lower the signal-to-noise ratio of the picked-up image.
Because of the need for an EMC measure, a conventional integrated circuit chip module employs a method of mounting an integrated circuit chip on a printed wiring board that is provided with an EMC measure design as disclosed in, for example, Japanese Patent Application Laid-open No. 2000-20573 (see paragraphs 0007 to 0009 and FIG. 1), No. 2002-26272 (see paragraph 0062 and FIG. 11), and No. 6-216272 (see paragraphs 0021, 0022, and FIG. 1).
According to the conventional integrated circuit chip module, an electric field is shielded and power source impedance is lowered to minimize a change range of voltage fall due to a change in the flowing current. In order to prevent a circuit signal from flowing to other circuits through a power source circuit, there has been employed a method that patterns of power source wires at a plus voltage side and a minus voltage side (hereinafter “a set of two power source wires”) formed on the printed wiring board are widened to provide plane-shape patterns. Further, there has also been employed a method that a printed wiring board is multi-layered and, and a set of two power source wires are allocated to two layers in the middle, thereby to easily realize a plane-shape power source pattern and a plane-shape ground pattern.
According to the integrated circuit chips mounted on the printed wiring board provided with the EMC measure, an electrode pad for a power source wire at a plus voltage side and a power source pad for a power source wire at a minus voltage side are not laid out adjacently in parallel. A pad having another function is disposed between the two power source pads, and the two power source pads are disposed separately at a distance. Therefore, on the printed wiring board, the respective power source wires are connected through bonding wires, and the power source wires are connected to a plane-shaped power source pattern and a plane-shaped ground pattern via respective via-holes.
However, according to the design of the conventional integrated circuit chip module, the module is designed by considering only an optimum layout within an integrated circuit chip. A layout of circuits within a chip taking an EMC measure into account, considering external parts of peripheral circuits, has not been carried out. A package has been designed by concentrating attention on the internal structure of the package. An EMC measure has been considered at the stage of installation, and a method based only on electromagnetic shielding has been employed. For example, the surroundings of a clock circuit, which produces much radiation, and all of a circuit unit are covered with a metal plate. As a result, according to the conventional method, a large scale has been required for the EMC measure, at high cost.
In other words, at the design stage of an integrated circuit chip module, when it is possible to realize a structure in coexistence with other integrated circuit chips without causing electromagnetic interference to other integrated circuit chips and without sufficient electromagnetic interference from other integrated circuit chips, a large scale is not required to provide an electromagnetic shielding measure if necessary. Further, it is also possible to minimize cost for this measure.